To the present date, synthesis of long-chain carboxylic acids containing up to about 33 carbon atoms in a straight chain have not proven to be useful economically when applied to large scale production. Most processes involve a keto-acid intermediate. Some older processes show very low yields and involve additions of various half esters, half-acid chlorides (or halides) to organometallic intermediates or beta-keto esters. While some other methods show good yields, they produce contaminated products. One aspect of the present invention is to produce these long-chain carboxylic acids and their alcohols economically with improved yields and purity.
Specifically, the process of this invention provides for the economical synthesis of 1-triacontanol. U.S. Pat. No. 4,150,970 discusses in detail the growth regulating effect of 1-triacontanol for plants.
U.S. Pat. No. 4,167,641 relates to a method for the preparation of long-chain carboxylic acids which can be readily converted to alcohols. However, the disclosed method of synthesis involves many reaction steps and requires extensive manpower and special equipment for purification.
The process of the present invention is designed for preparation of long-chain carboxylic acids and alcohols wherein cyclododecanone is reacted with morpholine in the presence of an acid catalyst to yield 1-morpholino-1-cyclododecene.
The present invention uses this enamine: ##STR1## as a basic starting material. The preparation of 1-morpholino-1-cyclododecene is described by W. Lendle et al in Chem. Ber. 100, 3996 (1967).
Compound (I) is reacted with acid halides of the type (II): ##STR2## wherein Z is a chlorine, bromine, iodine or fluorine radical and X is 0, 1, 2, 3, 4, or 5 to obtain long chain alcohols of type (V) according to the following representative scheme: ##STR3##
One advantage of the present invention over what is known in the art is that acid chlorides of type (II) are used, which are cheaper and more readily available than lignoceric acid (a linear carboxylic acid containing 24 carbon atoms).
An important difference in the present process over that of U.S. Pat. No. 4,167,641 is evidenced by the different products obtained at the compound (III) stage. A ring expansion has taken place in the present process to yield a 14-member .beta.-diketone with both keto groups in the ring as opposed to no ring expansion in the process of U.S. Pat. No. 4,167,641 and a .beta.-diketone with one keto group external to the ring.
Hunig & Buysch in Chem. Br. 100,4010 (1967) describe a method to cleave a 14-membered alkylated ketone in ethanol to yield the sodium salt of 13-keto-triacontanoic acid, however, the process is cumbersome in that multireaction steps are required and yields and purities are only moderate.
The applicant has unexpectedly discovered that the cleavage of the 14-member .beta.-diketone compound (III) can be accomplished with an alkali metal hydroxide in a solvent (i.e. diethylene or triethylene glycol), thus eliminating a separate step for the cleavage reaction in ethanol. Furthermore, it has been discovered that the cleavage and reduction steps can be carried out sequentially in one reaction vessel.